Problem: Which of these numbers is composite? ${3,\ 29,\ 37,\ 77,\ 83}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 3, 29, 37, and 83 each have only two factors. The factors of 77 are 1, 7, 11, and 77. Thus, 77 is the composite number.